Long cycle life microporous spherical carbon anodes for sodium-ion batteries derived from furfuryl alcohol

Spherical micron-sized carbon powders were synthesized from feedstock furfuryl alcohol and tested as anodes in sodium ion batteries (SIBs). A long cycle life of 1000 cycles is achievable with this carbon at C rate (3–4 mg cm−2 loading and i = 200 mA g−1) yielding a steady capacity of ca. 115 mA h g−1. The results from solid-state 23Na MAS NMR analyses of cycled electrodes indicate no correlation in voltage profiles with sodium site nature (graphene or nanopores), which is a new observation in SIB carbon anodes.